Effect of Inflow Swirl on the Sealing Effectiveness of Turbine Rim Seal

Abstract

Abstract Turbine inlet swirl condition is inherently present at the combustion chamber outlet and has an important influence on mainstream flow and gas ingestion. The sealing effectiveness and ingestion mechanism were numerically investigated using Unsteady Reynolds-Averaged Navier-Stokes (URANS) equations coupled with a fully developed shear stress transport (SST) turbulent model. Mass transfer analogy is utilized to simulate the hot gas ingestion and sealant egress by seeding CO2 into the air as a tracer gas. Simulations with mainstream inflow swirls of 0°, ±10°, ±20° were conducted and compared. Computational results indicate that at the same sealant flow rate, the sealing effectiveness increases significantly with the increase in the incidence angle at the leading edge of stationary vanes. When the non-dimensional sealant rate is 0.02415 and the incidence angle is increased from 0° to +10° and +20°, the sealing effectiveness at r/b = 0.958 on stationary disk is increased by 3.39% and 13.26%, respectively. The area-averaged sealing effectiveness of +20° incidence angles at the stationary and rotating disk can be increased by 12.02% and 5.19%, compared with the 0° incidence angle. The incidence angle near the vane leading edge affects the formation position of the horseshoe vortex, and ultimately affects the passage vortex. Therefore, the flow field in the rim seal clearance changes greatly. From axial and radial perspectives, the vortex due to Kelvin Helmholtz instability increases the blockage of axial rim seal clearance with the increase in incidence angle. From a circumferential perspective, as the incidence angle increases, a vortex structure is induced at the entrance of the rim seal, and the radial scale of the vortex decreases and the axial scale increases. All variations can gradually weaken the gas ingestion and improve the sealing effectiveness in the disk cavity. Based on fast Fourier transform (FFT) and analyzing the unsteady mass flow rate of ingress through the rim seal, the influence of the vortex due to Kelvin Helmholtz instability with a period of about 20 time-steps plays a major role in influencing sealing performance. The sealing effectiveness and flow pattern in the rim seal clearance have strong unsteady characteristics with this period.